The present invention relates to a high definition television transmission system, in which the image is divided into a plurality of parts, for each one of which a video data transmission mode making use of motion vector data may be used, the system being equipped, consequently, with a motion estimator to determine a motion vector for each one of the image parts, and means for transmitting on an associated digital transmission channel, data defining all the motion vectors of the parts for which such a vector is used.
The invention relates also to a high definition television transmission method, in which the image is divided into a plurality of parts, for each one of which a video data transmission mode making use of motion vector data may be used, said method comprising, consequently, a motion estimation to determine a motion vector for each one of the image parts, and a transmission on an associated digital transmission channel of data defining all the motion vectors of the parts for which such a vector is used.
It relates also to a high definition television receiver for representing transmitted images in which the image is divided into a plurality of parts, for each one of which a video data reproduction mode making use of motion vector data may be used, the motion vector data being received for each one of the image parts to be processed in this mode, said receiver being equipped with means for creating, from the motion vector data, an intermediate image between two images received consecutively, these means comprising, in particular, one or more memories for recording motion vector data.
The invention is in particular applicable in a system equipped with a motion estimator of the type referred to as BMA (Block Matching Algorithm), that is to say comprising first means for, in the presence of a pair of successive images, examining a part of one of the images by comparing it by turns with a series of parts of the other image to seek an identity or a similarity, these parts occupying a series of positions such that if in order to seek an identity or a similarity they were each displaced along one of the possible motion vectors, they would coincide with the examined part.
Such a system referred to as DATV (Digitally Assisted Television), in which data complementary to the video data and in particular the motion vectors are transmitted by digital means, is known from the paper entitled "Motion compensated interpolation applied to HD.MAC pictures encoding and decoding" by M.R. Haghiri and F. Fonsalas, presented at the "2nd international workshop on signal processing of HDTV", l'Aquila, 29 February-3rd March 1988.
In the system proposed by this document, the signal to be transmitted is created by a 50 Hz camera with an interlaced image of 1152 lines with 1440 pixels per line. This signal is considered to be sampled at 54 MHz; this is four times the frequency indicated in the Recommendation 601 of the CCIR. An encoding is used to reduce the sampling frequency by a factor of 4, with an associated digital data throughput which is as small as possible. To this end, the image is divided into a plurality of parts, in this instance squares of 16.times.16 pixels, and for each square, a transmission mode may be selected from among a plurality, one of these modes making use of a motion vector.
This document also describes a motion estimator of the BMA type, in which seventeen successive comparisons are undertaken in order to estimate motion, with maximum displacements of +3 pixels. The number of comparisons increases more or less as the square of the maximum amplitude of the displacements, and the method therefor rapidly becomes unusable for large motions.